Green, CPA, was engaged to audit the financial statements of Essex Co. after its fiscal year had ended. The timing of Green's appointment as auditor and the start of field work made confirmation of accounts receivable by direct communication with the debtors ineffective. However, Green applied other procedures and was satisfied as to the reasonableness of the account balances. Green's auditor's report most likely contained a(an)

a. Unqualified opinion.

b. Unqualified opinion with an explanatory paragraph.

c. Qualified opinion due to a scope limitation.

d. Qualified opinion due to a departure from generally accepted auditing standards.